Control system utilizing single point ignition



Sept. 16, 1952 E. WITZ EL Filed May a, 1947 F lm Se t. 16, 1952 E wn-z 2,610,680

CONTROL SYSTEM UTILIZING smcua POINT icunxou Filed May 8, 1947 2 SHEETS-SHEET 2 Patented Sept. 16, 1952 ,1 UNITED {STATES i O "con act. SYSTEM UTILIZING smote I OIN NIL QN Ernst VV-i tzel, lyi-ilwaukec, Wis, ass'ignoito Milwaukce Gas Specialty Company, -Milwaukee, Wis., a corporation of Wisconsin Application Maya, 1947, Serial no, 746380,

This invention relates in general, to ignition systems, and has particular relation to an improved single point ignition system for fuel burners.

While the particular "embodiment of the in:

vention which I shall describe "hereinafter in connection with the drawings is asingle point ignition system adapted for use with domestic gas ranges, it is to be understood that the invention is not limited to such use but may be employed for all simila'r purposes, for example, in connection with various commercial forms of apparatus having a baking oven burneLZhroiler oven burner, or other burner remotely located relative to the pilotburner. j

In the usual domestic gas range, the pilot burner is in the form of a single constantly "burning pilot located in juxtaposition'to the top burners at the upper part of the range, and the baking'oven, broiler, or like burners are located in the lower part of the "range. Although the top burners are usually provided with a constantly burning pilot burner for lighting the same, at the present time a match is usually employed for lighting the baking oven, broiler ojrlike burners, r t

The stoop'ing andhazards of lighting an' oven burner or the'like with 'a' match are Welljkn ow'r'i in the art.

On the other mm, a all gas ignition "system thews, SerialNo. 742,017, filed April 17,1947, and now Patent No. 2,578,l94, provl le an improved system of flash tubes and intermediate pilot means for assuring ignition of a pilot in junta,- position to the oven or like burner from a constantly burning top pilot; also improved-single point ignition systems wherein means, shown in the form of thermally responsive means, is

provided for extinguishing the intermediate pilot means and establishing a flow of ,fuel to the .oven or like aburner after a time :delay; following ignition of the burnerpilot, and improved thermoelectric ee'ntrol -'dev1ces and other unstruiiient'alities for accomplishing the new and auvantageous results therein setior th. r

7 In my copending application, Serial No. 7449-05, filed April 30, we' l/the time delay is obtained.v by an orifice limiting the escape o'f the air compressed by the'g'as line fpres'sure.

iOne'of the main-objects of the presenting vention is to provide a simple, improved and tion will appear from the renewing det ed -efiective single point ignition system which will provideft lre advantageous 'r'esult's' o'b'tained with the systems clisclosed and claimed in thefabove identified copending applications, and in which the time delay does not require thermally --rel= sponsivemeans and is "not dependent upon the gas pressure in the iuels-upply line.

Another objectof the invention is to provide 'a time delay which will prevent the newer :gas

to the burner whe'n artergscm operation the gas cook or other gas shut-on ineansis closed and inrnn'e'diate'lyopenedagain Another 'objectof the invention is to provide a, single'p'oint ignition-system {of the class de scrihed in whichth'e -fuel supply for the one or more intermediate pilots in definitely shut cit after a given time interval and independently of the valve controlling the supply of fuel to fthe main bu'rner.

I Another object of the .mventirm is toettuce a ewherejinth time delayls set into opergfion manual-1y by manipulation of me ges cock for other gas shut-oft means;

Another object f the invention is to provide m a system 'o'rthe class described, improved shut-off and itirne' delay means incorporated a single device "and a thermoelectric generfator (such as a thermocouple orthermopile) operated device adaptedtp be separately installed.

Another object of the invention is to provide a single point ignition system and instrumental'i'ties therein, as will hereinafter appear; hav

ing various feafturesfo,f novelty "andadv'antag'es, and whi are, a t cu rly .cha' iabtefized by their simplicity constr c'tion, their "eqcnomy in. manufacture anuiinsauamm, and their "er fectiveness in use.

Further. objects andadvantages of t e in endescription; taken m connection withit companying drawings which illustrate the ner of constructing and operating an illustrative e be imem of th n en o In thedrawi-ngs: e I I Figures-land -1-A are parts-oi adiagrammatlc the 3 right of Figure 1 and the line B--B of Figure 1A on the line A-A of Figure 1, form a complete diagrammatic view of one form of single point ignition system embodying the present invention; and

Figure 2 is a fragmentary sectional view through the shut-off and time delay device taken on the line 22 of Figure 1.

Referring now to the drawings, the burner is the baking oven, broiler, or other remote burner. It is usually located in the lower part of the rang or other appliance.

The pilot 2 is the constantly burning pilot. It may be, for example, the top pilot for the top burners of a gas range or other constantly buming pilot. The pilot 2 is usually located in the upper part of the appliance.

A fuel supply pipe 3 leads to the burner for the delivery of gaseous or other fuel thereto, for example. through a mixing chamber 4 to which air is admitted through adjustable air inlets (not shown) as well understood in the art. The flow of gas through the pipe 3 is controlled by a shut-off and time delay device 5 and by a thermoelectric generator (such as a thermocouple or thermopile) operated device 6.

The oven or like burner I is provided with an oven or like pilot I for igniting it. A flash tube 8 opens at its upper end directly beneath the flame 3 of the constantly burning pilot 2. This tube extends vertically downwardly from the pilot 2, and opens at its lower end at I directly above the flame H of an intermediate pilot I2. The intermediate pilot I2 is spaced laterally from another intermediate pilot l3 in juxtaposition or igniting relation with respect to the oven pilot 1. The lower end of the tube 8 has a branch |4 extending laterally therefrom and opening at its outer end at directly above the flame I6 of the intermediate pilot l3.

The shut-off and time delay device 5 comprises valve body parts 20, 2|, 22, 23, and 24. The valve body part 20 has an inlet 26, and valve body part 2| has an outlet 21. Contiguous sections of the fuel supply pipe 3 are connected to the inlet 26 and outlet 21.

Gas shut-off means, shown in the form of a gas cock 28, has, for example, a tapered plug part rotatable in the wall of valve body part 20 adjacent to inlet 26. The shut-off means 28 has port means at 29 adapted by turning of the shut-ofl. means to be placed in register with a passage 30 leading from inlet 26, and a passage 3| leading into a chamber 32. The shut-off means 28 is closed by turning it to position in which port means 29 is out of register with passages 30 and 3|.

It is to be understood that any other desired type of gas shut-off means may be employed in lieu of the gas cock 28, for example a remotely controlled solenoid or motorized valve. In such case the valve may be of other than the tapered plug form selected for illustration, and the form of its cooperating seat may vary accordingly.

A port 33 is adapted to place chamber 32 in communication with a chamber 34 separated from chamber 35 by a diaphragm 36 clamped marginally between valve body parts 2| and 22. A valve seat surrounds the end of port 33 adjacent to chamber 32 for cooperation with a valve 31.

Outlet 21 leads out from chamber 34. A passage 38 places chamber 32 in communication with chamber 35. A port 39 is adapted to place chamber 35 in communication with a chamber 40 separated from a chamber 4| by a diaphragm 42 clamped marginally between valve body parts 22 T chamber which embraces the wall 19.

and 23. A valve seat surrounds the end of port 39 adjacent to chamber 40 for cooperation with a valve 43.

Valve or valve facing 43, which is preferably of yielding material and disc-like form, is fixedly secured to a valve stem 45 at the axis of the diaphragm 42, which is likewise secured at its axis to the stem 45 and valve 43. Valve stem 45 passes down through abutment discs or plates 46 at the axis of diaphragm 36. A coiled spring 41 is interposed between abutment disc 46 and valve body part 22 adjacent to port 38.

At its lower end the stem 45 has a rounded head 48 for cooperation with a cam 49 on the inner end of a stem 50 which extends inwardly from shut-off means 28. Valve 31 is carried by stem 45 near the lower end of the stem. A coiled spring 5|, interposed between a flanged sleeve abutting cam 49 and valve body part 20, maintains the tapered plug part of gas shut-off means l8 seated in its bore in valve body part 20.

An outlet from chamber 40 is connected by a pipe or tube 55 with the intermediate pilots l2 and I3 for the purpose of supplying fuel thereto, as will presently appear. The constantly burning pilot 2 is supplied with fuel through a pipe or tube 56 connected at 51 with the fuel supply pipe 3 anterior of the shut-off and time delay device 5.

A perforated plate 58 and air filter 59 are clamped marginally between the outer end of valve body part 24 and a filter cover plate 60. A diaphragm 6|, clamped marginally between valve body parts 23 and 24, separates chamber 62 from chamber 63. Chamber 62 opens outwardly through the perforations in plate 58 and through air filter 59 and a port 64 in filter cover plate 60 to atmosphere. A passage 65 leads from chamber 62 to a port 66 which is adapted to open into chamber 63, as will presently appear. A valve seat surrounds the end of port 66 adjacent to chamber 63 for cooperation with a valve 61 secured to diaphragm 6| at the axis thereof.

A passage 66 opens from chamber 4| into chamber 63. A passage 66 opens from chamber 62 to a tapered bore 10 near the outer end there of. A passage 1| opens from the bore 10 near the inner end thereof into the chamber 4|. The communication between chambers 62 and 4| through passages 69 and H and bore 16, and thereby the time delay, is adapted to be adjusted by screw 12 screwed into valve body part 23 and having a tapered pin cooperating with the tapered bore 10. The outer end of screw 12 has a kerf or other means for engagement, for example, by a screw driver or other suitable implement for adjusting the tapered pin to any desired position.

The device 6, which is operated by the thermoelectric generator, comprises a valve body part 15 having an inlet 16 and an outlet 11. Contiguous sections of the fuel supply pipe 3 are connected to inlet 16 and outlet 11, for example, by connecting the section of the pipe 3 leading from the outlet 21 of the shut-off and time delay device 5 to the inlet 16, and the section of the fuel supply pipe 3 leading to the main burner to the outlet 11.

Internally, valve body part 15 has a generally L-shaped outlet chamber 18 having a longitudinally extending part in open communication with outlet 11 and a transversely extending portion defined by a cylindrical wall 79. An inlet chamber 60, in open communication with the inlet 16, terminates at its inner end in a generally annular aermeso "Tl'ie wall '19 'terminatesiinen annular valve "seat 8 L -An armature 82, "of 'disc like form, has a yielding or other suitable valve orfvalveifacing '83' adapted-to-seat against theseat 8| to shut off the flow of gas fromfthe inlet '18 .to outlet Tl through chamber 18. 3A? hood T8-t i's clamped.to the valve body part 'by a'union'nut 85,1ancl preferably'with a hood gasket therebetween;

In the illustrated embodiment of 'the invention, the I means i for operating "the valve 83, and more particularly the means vfor opening this valve, is in :the form o'f tan :electromagnet comprising a magnetjrame or :coil tspool ziifi'and a coil 81. .One'sideof the coil 1811s connected by a lead 88 to one of the :thermocoupleelements 89 of althermr'ncouple 88 or other suitable thermoelectric generator (such as a thermopile). The .otherelement 9i of'the thermocouple :88 is connected'by a lead 82tothe other side of'the coil .82.

The thermocouple 98 and lead connections therefor may be of the general character dis- .closed and claimedin'Oscar J .LeinsPatent No. 2,126,564, grantedAugustQ,1938,.or itmay be of any other suitablecharacter, or. in the form o'f-a ;thermopile or other thermoelectric generator. The thermoelectric generator has one or more hotjuncti'onsior example the hot junction93, which isgplaced imposition to belheated by the flames-94 and 94 of theintermediate pilot I3 and burner. pilot 1.

In the. illustrated embodiment of the: invention, theelectromagnethas a flux shell 95, and aspacer ring 88. The lower end of the coil spool 88 has a'naxialrecess, and disposed in this recess and interposed between spoolw88and armature 821 is a coiled spring-91 which operates to move armature '82 to position to seat valve 83 'on valve seat 81 when the electromagnet is deenergized. .Energization-of the electromagnetbyheating of the hot junction of the thermocouple 9.8 is .sufficient .to lift valve 83 to open position against the action of spring 91. A hood spring '98, interposed between the top of the spool 86 and hood 84, .seatsthe shell 95 in the valve bodypartat I80.

The operation :of the system shown in the drawings is as. follows: V l

When shut-off means. is turneditozclosed gposition,"cam'oractuator 49 lifts valvestem :45, thus. closing valve3'l and opening valve .43,fthereby openingthe gas .passage to intermediate Lpilots lland I3. No gas canfiow to the intermediate pilots at this time however,-since shut-.ofl means 28 is closed.

Now,'when gas cook or shut ofl" imeans'flza :is

turned to open position (seeFigure 1-) cam .49.re'-

leases valve-stem which may moverintoits lowest position (as viewed inFigure .1) after a fgiven time interval. The time interval or time delay is accomplished as follows: I

When valve 'stem 451s raised, air inchamber -'4l is'displaced by way of passage -68, valve61, passage 65, air filter '59 andpo'rt 64 to'atmos- 'phere. V'alvefi'lis'lifted against theflaction of'a springill! by means of excess'pressure inchamber 4L 'Now,'"whengas'cock or shut-"off device '28 is moved to open position, valve stem 45 is allowed to drop or move back to its lowest position with the'help of spring 41'. 'This produces .a suctionin chamber 4 l, and valve'fi'l will close tightly sdthat air may enter chamber 4| only through passages'SQ and'f'll and bore'lfl. Bore 1D is con- :tr'olle'dby tapered pin j'i2, -and theamount ofair permitted to enter can be adjusted accuratelyso that any-desired definite time-intervalwill elapse before waive :stem 45 iis tretumed. to fli 38, chamber 35,= port 39, chamber *40' and piperior tube 55 to the intermediate pilots l2 andti3. The unburned gas from :the intermediate pilots rises in the tube 8, which'ls-relatively:cool to permit this action. ."Asitreaches theifiam'eof constantly burning pilot 2, :the gas is ignited :and 'then :re-v cedes orflashes back .to .light the intermediate .pilots l2 and i3. w

-During the time delay, thermocouplarthermopile or other .thermo,elec.tricgenerator been :heated by intermediate pilot 'I3"'to.c.energize magnet coil .87 of valve 6 sufliciently to actuate thevalve 83 .to' open-position. Gas is :anowrad- :mitted to even burner i 211611130 iburner'pilotfzl which is. ignited by intermediateipilot l3 1 8116101).- 'eratesfto ignite the toven'burner. .Burner pilot 51 now takes over the work of heating the thermoelectric generator 98.

Gas'flow to oven burner .l and burnerpilot 1 .is'established when," with :valve .83 open, .theavalve stem 45 ;returns toiits lowest 'positionthereby opening valve 31 and closing valve '43. The closing ofvalve 43 shuts off the supply of fuel to intermediate pilots 12 and l3.vand, as'airesult, unnecessary or undesirable heating of therfl'ash tube or other parts is :avoided and economyzis provided. The flash tube is'always iniaicoollion- 'dition, and *proper ignition is assured. .Inrorder to assure an'early :supply of gas'to burnerpilo't :1 before intermediate pilots I2 and I3 are textinguished, the .valves' are: arranged :so :that valve 31 will open before, and preiera'blyfa few'seconds before, valve -43 is closed. This is due'to :the spacing of the valves 31 'and43 apart axially-a greater distance than their :cooperating valve seats, and to-the'fact thatthe valve 31 begins'to open upon initial downwardxmovement of the stem 45 as it is'viewed in Figure '1; whereas 'at this time the valve 43 moves toward but .has :n'ot reached-- full closed position. a

The time ,delay'prevents thefiowiofggas tothe 'burner when after some'operationthe gas "cook "or other gas shut-offmeans isaclosedand immecouple or other thermoelectric generator to :cool "and deenergize andclose valve 6 so that in case the flash tubeisystem should fail'to function, the valve 6 will be closed before valve 31'opens.

The sequence of operations shows" that intermediate pilots Hand I3" are definitely closed to gas supply after the time delay, no matter vwhetherthey have been ignited ornot; thusno gas can escape irrcase of. flash tube failure. "The cam arrangement at i -represents only one-of many, solutions within the scoperof the present invention for liftingthe valve'tstem 45. and'opierating, the. shut-i-ofi, means 28 simultaneously. t

. .1Therefore' the ..-embodiment:cr :thezinvention 7 shown in'the drawings is for illustrative purposes only, and it is to be expressly understood that said drawings and the accompanyingspecification are not to be construed as a definition of the limits or scope of the invention, reference being bad to the appended claims for that purpose.

I claim:

1. In apparatus of the class described, in com- :bination, fuel supply means for supplying fuel to a main burner, to a constantly burning pilot burner and to intermediate pilot burner means, shut-off means in said fuel supply means and operable to establish and shut off the supply of fuel to the main'burner and to said intermediate pilot burner means, an intermediate pilot burner valve for controlling fuel admission to the intermediate pilot burner means and'operable to open position by actuation of said shut-off means to closed position, a main burner valve for controlling fuel admission to the main burner and operable to closed position by actuation of said shut-off means'to closed position, means for actuating said intermediate pilot burner valve to closed position and said main burner valve to open position when said shut-off means is actuated to open position, and time-delay means coacting with said shutoff means whereby operation of said time delay means is initiated by operation of said shut-off means to open position, said time-delay means coacting with said intermediate pilot burner valve and with said main burner valve, whereby to'produce a time delay after the opening of said shutoff means before opening of said main burner valve 'and closing of said intermediate pilot burner valve.

2. Apparatus according to claim 1 wherein the time delay means comprises a device having a chamber provided with means operated by said shut-off means for displacing the air from said chamber and wherein there is a restricted inlet to said chamber from atmosphere for delaying the establishment of fuel supply to the main burner and shut off of the fuel supply to the intermediate pilot burner means.

3. Apparatus according to claim 1 wherein the time delay means comprises a device having a chamber provided with'means operated by said shut-off means for displacing the air from said chamber and wherein there is a restricted inlet to said chamber from atmosphere for delaying the establishment of fuel supply to the main burner and shut off of the fuel supply to the intermediate pilot burner means, and means for adjusting saidrestricted inlet.

4. Apparatus according to claim 1 wherein there is an igniting pilot burner in juxtaposition to said intermediate pilot burner means and said main burner, an electroresponsive valve in the fuel supply line for the main burner, and a thermoelectric generator subject to the heat of both said intermediate pilot burner means and said igniting pilot burner and connected in circuit with said electroresponsive valve for operation of said valve to open position by the heating of said thermoelectric generator.

5. In apparatus of the class described in combination, a device having a diaphragm with a fuel supply chamber on one side and an air chamber on its other side, said air chamber having an closed position shutting off the entry of fuel into said fuel chamber, a fuel supply line, shut-0E means in said fuel supply line, and means for opening said last valve by operation of said shutoff means to, closed position, the restricted entry of air into said air chamber acting to maintain said valve open for an interval of time upon operation of said shut-off means to open position.

6. In apparatus of the class described. in combination, a device having a diaphragm with a fuel supply chamber on one side and an air chamber on its other side, said air chamber having an outlet opening from said chamber and a restricted inlet opening into said chamber from atmosphere, a valve for said outlet, a valve carried by said diaphragm, said valve having open position for entry of fuel into said fuel chamber and closed position shutting off the entry of fuel into said fuel chamber, a fuel supply line, shut-off means in said fuel supply line, means for opening said last valve by operation of said shut-off means to closed position, the restricted entry of air into said air chamber acting to maintain said valve open for an interval of time upon operation of said shut-off means to open position, and means for adjusting the restricted entry of air into said air chamber.

7. Apparatus according to claim 6 wherein the means for adjusting the restricted entry of air into said air chamber comprises a tapered duct and a cooperating adjustable tapered pin.

8. In apparatus of the class described, in combination, a valve body having a fuel inlet chamber and a first fuel outlet chamber, intermediate pilot burner means connected to receive fuel from said first fuel outlet chamber, a pair of intermediate fuel chambers one adapted for delivering fuel to said first fuel outlet chamber, a main burner connected to receive fuel from the other intermediate fuel chamber, passage means leading from said fuel inlet chamber to the intermediate chamber for delivering fuel to the intermediate chamber which delivers fuel to said first fuel outlet chamber, a first valve controlling communication between said fuel inlet chamber and the intermediate fuel chamber for connection with the main burner, a second and oppositely seating valve controlling communication between the other intermediate fuel chamber and said first fuel outlet chamber, a shut-off device, and means actuated by operation of said shut-off device for moving said first valve to closed position and said second valve to open position.

9. Apparatus according to claim 8 wherein there is a time delay device comprising a chamberprovided with means for displacing air from said chamber and wherein there is a restricted inlet to said chamber from atmosphere for delaying closing of said second valve and opening of said first valve.

10. Apparatus according to claim 8 wherein there is pilot burner means, a fuel supply line, an electroresponsive valve in said fuel supply line, and a thermoelectric generator subject to the heat of said pilot burner means and connected in circuit with said electroresponsive valvefor opening said valve by heating of said thermoelectric generator. 7

11. In apparatus of the class described, in combination, fuel supply means for supplying fuel to a main burner, to a constantly burning pilot burner and to intermediate pilot burner means. shut-off means in said fuel supply means operable to establish and shut-off the supply of fuel to the main burner and to said immediate pilot burner means, an intermediate pilot burner valve for controlling fuel admission to the intermediate pilot burner means and operable to open position by actuation of said shut-off means to closed position, a main burner valve for controlling fuel admission to the main burner and operable to closed position by actusaid time-delay means coacting with said inter- I mediate pilot burner valve and said main burner valve whereby to produce a time delay after the opening of said shut-off means before opening of said main burner valve and closing of said intermediate pilot burner valve, and an electrorespon sive valve in the fuel supply means for supplying fuel to the main burner, said electroresponsive valve being located on the posterior side of the main burner valve.

12. A safety shut-off device for a burner apparatus comprising, in combination, a valve body having a fuel inlet and a first fuel outlet for delivering fuel to both a main burner and an igniting pilot burner, said valve body having a second fuel outlet for delivering fuel to intermediate pilot burner means, a first valve operable to shut off fiow of fuel through said first fuel outlet. a second valve connected for operation with said first valve and operable to shut off fiow of fuel through said second fuel outlet, actuating means for actuating said valves together in one direction to close said first valve and open said second valve, said valves being operable in the opposite direction upon release of said actuating means to open said first valve and close said second valve. said first valve being arranged to open before said second valve closes, and time delay means for delaying closing of said second valve for a timeinterval after opening of said first valve.

13. A safety shut-off device according to claim 12 wherein the actuating means for actuatingthe valves in a direction to close the first valve and open the second valve comprises a shut-off" valve positioned to control the delivery of fuel to the safety shut-off device through its inlet.

14. A safety shut-off device according toJclaim 12 wherein the actuating means for actuating the valves in a direction to close the first valve and open the second valve comprises a shut-off valve positioned to control the delivery of fuel to the safety shut-off device through its inlet, said shut-off valve operating to closed position when actuated to close the first valve and open the second valve.

15. A safety shut-off device according to claim 12 wherein the actuating means for actuating the valves in a direction to close the first valve and open the second valve comprises a shut-off valve positioned to control the delivery of fuel to the safety shut-off device through its inlet, said shutoff valve operating to closed position when actuated to close the first valve and open the second valve and, when operated to open position, releasing said first and second valves for opening of said first valve and closing of said second valve under control of the time delay means.

16. A safety shut-off device according to claim 12 wherein the time delay means comprises a de vice having a chamber provided with means for displacing air from said chamber by actuation of the first valve to closed position and the second valve to open position, said device aving a restricted inlet opening into said chamber.

17. A safety shut-off device according to claim 12 wherein the time delay means comprises a device having a chamber provided with a diaphragm connected for actuation with the first and second valves for displacing air from said chamber by actuation of the first valve to closed position and the second valve to open position, said device having a restricted inlet opening into said chamber. 18.'A safety control device for burner apparatus of the class wherein there is a constantly burning pilot burner, a main burner remote from said constantly burning pilot burner, an igniting pilot burner in juxtaposition to the main burner for igniting the same, intermediate pilot burner means located between the constantly burning pilotburner and the igniting pilot burner for assuring ignition of the igniting pilot burner from the constantly burning pilot burner, a first fuel sup-' ply pipe for delivering fuel to both the main burner and the igniting pilot burner, a second fuel supply pipe for delivering fuel to the intermediate pilot burner means, a thermoelectric safety shutoff device positioned in the first fuel supply pipe and operable to shut off the fuel supply to the main burner and to the igniting pilot burner, a thermoelectric generator connected in circuit with the thermoelectric safety shut-off device and positioned to be heated both by the igniting pilot burner and the intermediate pilot burner means, said safety control device comprising a valve body having a fuel inlet, a first fuel outlet for delivering fuel to said first fuel supply pipe and a second fuel outlet for delivering fuel to said second fuel supply pipe, a pair of connected valves one for shutting off the flow of fuel through said first fuel outlet and the other for shutting off the fiow of fuel through said second fuel outlet, means for actuating said valves together in onedirection to close the valve which shutsoif fiow of fuel through said first outlet and to open the valve which shuts off flow of fuel through said second outlet, means for actuating said valves in the opposite direction upon release thereof to open the valve which shuts off flow of fuel through said first outlet and to close the valve which shuts off fiow of fuel through said second outlet, the valve which shuts off fiow of fuel through said first outlet being arranged to open before the other valve closes, and time delay means for delaying closing of the valve which shut off flow of fuel through said second outlet until the thermoelectric safety shut-off device is operatively energized by the heat of the igniting pilot burner on the thermoelectric generator.

ERNST WITZEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

